A conventional coal-fired boiler includes a furnace that is hollow and is installed in the vertical direction and a plurality of combustion burners that are disposed in the wall of the furnace in the circumferential direction in a plurality of vertical rows. The combustion burners are supplied with a fuel-air mixture of pulverized coal (fuel) obtained by pulverizing coal and primary air and with secondary air at high temperature, and inject the fuel-air mixture and secondary air into the furnace to form flames. This operation enables combustion in the furnace. The furnace is connected with a flue at an upper portion. The flue is provided with heat exchangers, such as a superheater, a reheater, and a fuel economizer, for collecting heat of flue gas, and heat is exchanged between the flue gas produced by combustion in the furnace and water, thereby generating steam.
Examples of such a combustion burner of the coal-fired boiler are disclosed in the Patent Documents described below. The combustion burners disclosed in the Patent Documents each include a fuel nozzle through which fuel gas obtained by mixing pulverized coal and primary air can be blown, a secondary air nozzle through which secondary air can be blown from the exterior of the fuel nozzle, and a flame stabilizer that is provided on an axial center side at a distal end of the fuel nozzle. The flow of concentrated pulverized coal collides with the flame stabilizer to stably enable low NOx combustion in a wide load range.